This invention involves heat insulation for building structures whereby the walls, roof, ceiling, floors and other partitions of the building are insulated with flexible sheets of heat insulation material. More particularly, this invention involves heat insulation material that utilizes, in various combinations, phase change material, heat reflective material, dead air space, and fibrous blanket material, for use alone or in combination with other heat insulation materials in a building structure, to retard the transfer of heat between adjacent spaces about a building structure. Also, the method of making cell blanket heat insulation with a layer of phase change material is disclosed.
Heat insulation material placed in walls, ceilings, roofs, floors and other areas about a building typically comprise fibrous blanket insulation, such as elongated blankets formed of fiberglass. The principle of the blanket insulation is to form dead air spaces that provide insulation against convection and conduction heat transfer. The blanket insulation can be formed in small xe2x80x9cclumpsxe2x80x9d and blown into spaces such as into the attics of residential homes and other areas about building structures, and also can be made into elongated blankets formed in a specific width and thickness that are suitable for placement between parallel joists, studs, rafters, purlins and other parallel support structures that are uniformly spaced apart. The elongated blanket, such as a fiberglass blanket, usually is supplied in reels and is cut to the desired length at the job site for placement between the parallel structures.
Fiberglass is one of the more desirable materials for forming blanket insulation because it holds its shape and traps a substantial amount of air between its fibers to form the dead air spaces. However, the fiberglass alone does not provide adequate heat insulation against radiant heat transfer.
In the recent past, an additional sheet of radiant heat reflective material has been applied in building structures, sometimes in combination with other materials such as blanket material. The reflective material, such as aluminum foil, functions as a reflective surface for reflecting radiant heat, thereby functioning as a barrier to radiant heat transfer, and enhancing the insulation capabilities of the other heat insulation materials.
One of the problems with the above noted heat reflective insulation is that when reflective surfaces of the heat reflective foil engage another surface, such as an adjacent layer of insulation material or the structure of the building, the foil loses at least some of its ability to reflect heat. A space, such as a dead air space, must be maintained adjacent the foil in order for the foil to function as an effective heat reflector.
Another problem with the use of reflective surfaces in combination with other insulation materials for heat insulation is that if the surface of the reflective sheet material should become dirty from an accumulation of dust, trash, fibers, vapor, etc., the reflective sheet loses its ability to reflect radiant heat, and therefore loses its insulation value.
Another insulation innovation that has been developed in the recent past is the use of phase change material (xe2x80x9cPCMxe2x80x9d) in combination with other insulation materials. The PCM loses heat when it changes phase from a liquid to a solid and absorbs heat when it changes phase from a solid to a liquid. These changes of phase occur at a substantially constant temperature for the PCM. The net result is that when the PCM is used in a roof structure, for example, and the outside temperature begins to rise to a level higher than the phase change temperature, the PCM will remain at its phase change temperature as the PCM changes phase from a solid to a liquid. In the meantime, the PCM absorbs heat from the outside, warmer atmosphere without changing its own temperature or influencing a change of temperature in the inside atmosphere of the building structure. This effectively delays the transfer of heat from outside to inside of the building structure, reducing the load to be carried by the conventional air conditioning system of the building structure.
Likewise, the reverse is true when the outside temperature becomes lower than the phase change temperature of the PCM. The PCM begins to change phase from liquid to solid at a substantially constant temperature, gradually giving up its heat to the outside, cooler atmosphere, thereby delaying the transfer of heat from the warm interior of the building to the cooler outside atmosphere.
The use of PCM as an insulator for building structures is disclosed in U.S. Pat. No. 5,626,936, which is incorporated herein by reference.
Although the use of PCM has been disclosed in the prior art as being used as an insulator for building structures, the production and installation of insulators that include PCM is still somewhat expensive and not appreciated by most in the industry.
It is to these problems that this invention is addressed.
Briefly described, the present invention comprises an improved heat insulation assembly for placement in and for becoming a part of a building structure, for insulating the structure from conduction, convection and radiation heat transfer through the wall structures of the building. This includes vertical walls, ceilings, roofs, floors, and other partitions that separate the interior temperature controlled spaces from outside uncontrolled temperature spaces, generally referred to herein as xe2x80x9cwall structures.xe2x80x9d
In the disclosed embodiments, radiant heat insulation is used, either alone or in combination with other types of heat insulation. Also, phase change material (xe2x80x9cPCMxe2x80x9d) is used in combination with other heat insulation materials.
The radiant heat insulation includes heat reflective sheet material, such as radiant heat reflective metal foil, radiant heat reflective metalized plastic sheet material, and plastic material coated with reflective substances such as metal. More specifically, the reflective material can be formed of the group consisting essentially of metalized polyester, metalized polyethylene, metalized polyvinyl chloride, and metalized polypropylene. Typically, foil and other radiant heat reflective sheet materials are silver in color, or other efficient radiant heat reflective colors. The reflective surface of the sheet is maintained in a spaced relationship with respect to the next adjacent structure, and is enclosed in a space that protects the reflective surfaces of the reflective sheet from the accumulation of dirt, dust, insulation fibers, vapor and other things that are likely to occlude or diminish the reflective properties of the reflective surface of the reflective sheet.
In addition to reflective insulation, the invention includes use of phase change material in combination with the reflective material. Phase change material can be any material that changes between a liquid state and a solid state in response to the change in temperature, when the temperature rises across the phase change temperature of the PCM or decreases from a level higher than to a level lower than the phase change temperature of the PCM. PCM suitable for use can include calcium chloride hexahydrate, sodium sulfate, paraffin, Na2SO4.10H2O, CaCl2.6H2O, NaHPO4.12H2O, Na2S2O3.5H2O, and NaCO3.10H2O.
An example of the use of PCM as a heat insulator is when the PCM is placed in an exterior wall or attic of a building and the outside temperature rises from a level substantially lower than the phase change temperature of the PCM to a level substantially higher than the phase change temperature of the PCM. As the temperature exceeds the phase change temperature of the PCM, the PCM remains at the same temperature as it absorbs heat that causes the PCM to change phase from solid to liquid. This has the effect of delaying the transfer of heat from the warmer atmosphere to the cooler interior of the building.
In the reverse situation, the outside temperature decreases from substantially higher than to a level substantially lower than the phase change temperature of the PCM, and as the PCM is cooled, it gives up heat in response to its changing of phase from liquid to solid. Again, this delays the transfer of heat emitted from the interior of the building to the cooler atmosphere.
This invention includes a combination of heat reflective insulation and phase change insulation in the form of a cell blanket, whereby superposed cells of phase change material and of dead air space are formed by overlying sheets that include a surface of radiant heat reflective material, such as aluminum foil.
In one embodiment of the invention, the cell blanket is formed with an inner layer of PCM cells and opposed outer layers of dead air cells, with the dead air cells and the overlying sheets that form the cells providing both protection for the PCM cells and protection for the radiant heat reflective surfaces, so as to avoid occlusion of the reflectivity of the heat reflective surfaces.
Other arrangements of the cell blanket can be utilized, such as only a single layer of dead air cells adjacent a single layer of PCM cells, and other combinations of superposed PCM cells and dead air cells including the heat reflective surfaces.
The cell blanket described above can be used alone or in combination with various other insulation structures, such as gypsum board, fibrous blanket insulation, between the purlins of an industrial building, in new construction, and in old construction so as to supplement the previously applied or substitute for the previously applied insulations.
The cell blanket is formed in a continuous process by advancing multiple plies of sheet material into superposed relationship along a processing path with the plies of sheet material including a pair of juxtaposed inner sheets and a pair of outer sheets, with the inner sheets positioned between the outer sheets. The sheets are progressively connected together with a plurality of parallel seams in the sheets that extend along the processing path. The connection of the sheets can be made by the application of heated rollers against the superposed sheets, which fuses seams in the sheets that extend longitudinally of the path along which the sheets are advanced. The progressive connection of the four sheets forms inner channels between the inner sheets and outer channels positioned on the opposite sides of the inner channels. As the inner channels are formed, they are filled with phase change material, preferably in the liquid state. As the inner channels are filled with phase change material, the outer channels that straddle the inner channels are filled with gas, preferably air. Once the channels have been filled with PCM and gas, the work product is passed adjacent laterally extending rolls that divide the channels into discrete cells, forming an array of cells, with the cells filled with phase change material positioned between the cells filled with gas. This completes the formation of the cell blanket, by which layers of cells are formed, with at least one layer of cells including a PCM and other layers of cells being filled with gas. The radiant heat reflective surfaces of the sheets of material that form the cell blanket are positioned adjacent the dead air cells, and the space occupied by the dead air protects the reflective surfaces from the accumulation of dust, dirt, fiber, or moisture, and from engagement with other surfaces so as to avoid occlusion or deterioration of the reflective surfaces of the sheet. This tends to prolong the reflective life of the sheet material and, therefore, the capacity to function as radiant heat insulation.
Another feature of the invention is that the superposed layers of sheet material that form the cell blanket have a continuous coating of heat reflective material, so that the array of cells that extends across the length and breadth of a cell blanket form a substantially continuous layer of radiant heat reflective sheet material about the length and breadth of the blanket.
Preferably, the heat fused seams formed in the cell blanket that divide the cells from one another are relatively thin when compared with the length and width of the cells, providing a relatively large cell area in comparison with the area occupied by the seams between the cells.
In addition to the insulation offered by reflective sheet material and the PCM, the sheets that form the cells and the gas within then cells provide both convective and conductive heat insulation.
Preferably, the cell blanket is formed of support sheets that are of heat fusible material, such as polyester and polypropylene. In situations where the fusion of the layers of sheet material is not practical, adhesive bonding of the seams is possible.
Thus, it is an object of this invention to provide an improved heat insulation blanket for use in insulating adjacent spaces from each other, which includes layers of superposed cells, with the different layers of cells containing different insulation materials.
Another object of this invention is to provide an improved cell blanket for use in insulating wall structures and the like, and which includes layers of arrays of cells, with one layer of cells including a phase change material and another layer of cells including a different insulation material.
Another object of this invention is to provide an improved cell blanket for insulating wall structures and the like of a building, which includes superposed layers of cells, with one layer of cells including heat reflective sheet material facing a dead air space, and another layer of cells including another heat insulation material.
Another object of the invention is to provide a cell blanket that includes phase change material and heat reflective material, with both the phase change material and the heat reflective material being protected from contact by other objects.
Another object of this invention is to provide a method for expediently and inexpensively producing the cell blankets described herein.
Other objects, features and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings.